Shock wave metal forming method and apparatus



July 17, 1962 F. E. ZEIGLER 3,044,430

SHOCK WAVE METAL FORMING METHOD AND APPARATUS Filed Oct. 28, 1957 /6 /25 MI I 4 Sheets-Sheet 1 INVENTOR. /6. Z. :ea/vz 5 25/6452 July 17, 1962 F. E. ZElGLER 3,044,430

SHOCK WAVE METAL FORMING METHOD AND APPARATUS Filed Oct. 28, 1957 4 Sheets-Sheet 2 lllmllw I L I INVENTOR. Fem/z 5. 2/5/6452 July 17, 1962 F. E. ZEIGLER 3,044,430

SHOCK WAVE METAL FCRMING METHOD AND APPARATUS Filed Oct. 28, 1957 4 Sheets-Sheet 3 'IIIIIIIIIIIII INVENTOR. flea/we 5. 25/6452 syyj fg z July 17, 1962 F. E. ZEIGLER 3,044,430

SHOCK WAVE METAL FORMING METHOD AND APPARATUS Filed Oct. 28 1957 4 Sheets-Sheet 4 A I /0/- I V 79V 76 INVENT OR. rein/z 5. 25/6452 BZQ/WM United States Patent O This application relates to metal forming and particularly to a method of and apparatus for using explosive shock waves as the forming force rather than pressure waves.

The forming of metals by pressure dies and by explosive charges is known, the latter using punches, dies, draw rings, and extra heavy constructions. The explosive charge pressure wave method of forming metal is limited to small items and items of light material. This is because the explosive forces are contained within a chamber whose strength must be in proportion to the size of the explosive charge, size of the part in relation to the chamber size, and thickness of the metal being formed. Thus, the container for the explosive charge using pressure waves becomes impractical for forming large metal elements. For instance, the pressures in a closed container when using explosive charges are often in the neighborhood of 30,000 to 50,000 pounds per square inch. The physical containment for such a charge for even a few seconds time requires massive steel containers similar to the construction of the firing chambers of large calibre guns.

The herein described invention uses shock waves or forces rather than explosive pressure waves or forces, which permit the elimination of size limitations in the rapid forming of metals. It also eliminates high pressure containers by allowing the pressure to immediately escape into the atmosphere, only the shock waves being utilized to form the metal. It also eliminates many of the hazards involved in closed container explosions. With the invention, brittle metals may be formed by the rapid application of shock waves where such metals would crack or fracture when formed by a slower process.

The present invention permits control of the shock waves by providing adjustable positioning of the explosive charge and in one modification the adjustment of the openings between the explosive charge area and the atmosphere. The invention also contemplates a reflector for concentrating the shock Waves on the metal to be formed, thus increasing the efficiency of the apparatus and reducing the explosive charge required. The invention will permit the forming of not only brittle metals but also the forming of stainless steels of many varieties and other metal alloys.

The principal object of the invention, therefore, is to facilitate the rapid forming of metals.

Another object of the invention is to provide an improved method of and apparatus for rapidly forming metals by explosive shock waves or forces.

A further object of the invention is to provide an improved method of and system for controlling the rapid forming of various types of metals by explosive shock waves or forces.

A better understanding of this invention may be had from the following detailed description when read in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of one modification of the apparatus embodying the invention;

FIG. 2. is an elevational view of the apparatus shown in FIG. 1;

FIG. 3 is an end view of the apparatus shown in FIGS. 1 and 2 and taken along the line 3-3 of FIG. 2;

FIG. 4 is a partial view of the apparatus shown in FIGS. 1 and 2 and taken along the line 4-4 of FIG. 1;

a 3,044,430 Patented July 17, 1962 FIG. 5 is a diagrammatic elevational view of another modification embodying the invention;

FIG. 6 is a cross-sectional view of the modification shown in FIG. 5;

FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. 6;

FIG. 8 is a view partially in cross section of another modification embodying the invention;

FIG. 9 is a cross-sectional view taken along the line 99 of FIG. 8; and

FIG. 10 is a view taken along the line 10- 10 of FIG. 8.

Referring, now, to the drawings in which the same numerals identify like elements, a supporting structure 5 has two dovetail rails 6 and 7 on which are mounted two die units or blocks shown generally at 9 and 10, these units being adjustable along the rails 6 and 7. Each unit is identical so that the shock waves from an explosive charge 12 may form two pieces of material 15 and 15' simultaneously. The pieces 15 and 15' may be supported in any suitable manner, such as by slidable yokes l8 and 18'. In describing the units 9 and 10, prime numbers will be used for duplicate elements in each unit. That is, unit 9 has its die block 13, and unit 10 has its die block 13' mounted on respective bases 14 and 14" slidable along the rails 6 and 7 and attachable thereto in any suitable manner.

In describing unit 9, hydraulic cylinders 16 and 17 connected to air or oil supply pipes 19 and 20 control the movement of a draw ring 21 with respect to the die block 13, the draw ring being pulled toward the die block 13 by the rods 23 and 24 connected to adjusting rings 25 and 26 connected to die ring frame members 27 and 28. Valves such as shown at 29 control the actuation of cylinders 16 and 17.

Around the circular openings of the cavity 30 is an O ring seal 32, as shown more clearly in FIG. 4. When the hydraulic cylinders 16 and 17 are actuated, the draw ring 21 forces the piece of material 15 to be formed against the O ring seal to insure obtaining a vacuum within the cavity 30. This vacuum is produced by vacuum pumps (not shown) attached to conduits 34 which are connected with the cavity 30 by conduits 35 through the die block as shown in FIG. 4. To eject the formed I piece of material 15 from the die, a hydraulic knock-out ejector cylinder 36 with its plunger 37 is actuated. Although the unit 9 has just been described, the prime nur'nbered elements in unit =10 are identical, FIG. 4 being a cross section through the unit 10 having the prime numbers. To permit adjustment of the units 9 and 10, the air or oil couplings thereto are all flexible, it being understood that the units may be tightened to the rails after adjustment thereon.

The explosive charge 12 is mounted on a bracket support 40 and suspended on an adjustable arm 41 so that it is in the center of the pieces of material 15 andv 15 to be formed. Although two die blocks are shown to more fully utilize the shock waves from the charge 21, it is to be understood that a single die block may be used.

In the operation of the above described unit, units 9 and 10 are adjusted on the rails 6 and 7 and an explosive charge used in accordance with the type' and weight of the pieces of material 15 and 15' to be formed. When this adjustment is made, the cylinders 16, 17, 16 and 17' are actuated to bring the draw rings 21 and 21" in contact with the pieces 15 and 15', which, in turn, are pressed against 0 rings 32 and 32' to seal the cavities 30 and 30'. The cavities 30 and 30 are then exhaustedof air after which the explosive 12 is detonated. Since the explosive is exposed to the atmosphere, substantially only the shock waves, as indicated by arrows 33 in FIG. 4, will impinge upon the pieces 15 and'15' to force them into the die cavities 30 and 30. This will be accomplished very rapidly to permit brittle materials to be formed without fracturing. After the pieces'have been formed, the ejectors 36 and 37 and 36' and 37 are actuated to force the formed pieces 15 and 15' out of the dies after the draw rings 21 and 21' have been removed from the die blocks. 'The apparatus is then ready for new pieces of material and the cycle just described repeated after the replacement of a new explosive charge 12.

The force of the'draw ring againstfthe outer periphery of the metal to be formed prevents wrinkling and buckling similar to the action of a draw ring in a double action' press. The absence of air in the die cavity will prevent pressure build-up or pressure to be overcome by the shock waves. V I

The explosive charge may be low velocity propellants, such as black or smokeless powder, or high velocity propellants such as Primacord or fuse material having an explosive core of pentaerythritol tetranitrade enclosed within a waterproofed textile 'coveringJ This material may be purchased in variable grain size and may be cut to a predetermined length to correspond to the force'required of'the shock waves. 'The material, being-flexible, may be shaped by binding or coiling around a cardboard or papier mache form. The explosives can be detonated by the use of commercial blasting caps or other suitable means attached to electrical power conductors connected to a suitable power source over switches. I

Referring, now, to FIGS. 5 and 6, a second modification' of the apparatus of FIGS. 1 to 4, inclusive, is shown which will produce tapered cylindrical forms by explosive shock waves. In this modification, a base carries a dovetail rail 46 on which is mounted a pair of explosive charge carriers 48 and 49 having wave reflecting cavities 50 and 51, respectively. and are mounted to be partially within the cavities 50 and 51, respectively, and partly outside the cavities and are adjustable on rods 57 and 58, respectively. Mounted on asplit ring bracket 60 on rail 46 is a split die 61 within which is a piece of material 62 to be formed,

The explosive charges 54 such as metal. After the adjustmentof the explosive charges 54 and 55, as shownrin F-IG. 6, has been made,

the charges are detonated by the closing of a key 64 in a circuitincluding a power source 65 and conductors 66 which connect both the 'explosivecharges 54.and 55 either in series or in parallel so that both charges will be discharged simultaneously. FIG. 5 shows the piece 62 before forming, and FIG. 6 shows the piece after forming. After forming, the sections of die 61 and suphaving a wave reflecting cavity 72 therein. The shell 71 is of sufiicient thickness to withstand the shock waves of the explosion and is of a size large enough toform certain desired material; It is supported on a cantilever bracket support 74 into the upper end of which is threaded a member 75 attached to the shell 71. with IE1 speot to a die supporting base 76. Within the member 75 is a charge supporting rod 78 to adjustably position the charge within the cavity 72, the rod having a blocking and sealing unit 79 at the upper end of mem- -ber75.

Near the mouth of the shell 71, is a row of openings 82 adjustable'over which is a ring 81 also having a series of similar size openings 83 therein. By adjustment of the ring 81, the release of pressure resulting from the explosion in the cavity '72 to the atmosphere is controlled.-

That is, the area of communication between the cavity' I and the free atmosphere is readily adjustable to accom modate different types and thicknesses of materials "being formed. The lower edge of the shell 71 has a circular flange 85 to which is attached a resilient disc or diaphragm 86, such as rubber, and held in position by a clamping ring 87 and bolts '88. Thus, the opening of the. shell 71 is sealed by the rubber diaphragm 86. Positioned on the block 76 is a rectangular die 90 and a circular die 91, the die 90 supporting a work piece 92 held in position by a pin 93. 0n the die 91 is a work piece 95 which rests upon an O ring seal 96, the space within the die 91 being evacuated by a vacuum pump (not shown) connected to a conduit 98. The charge 70 is detonated over con ductors connected to power supply 101 when the switch 102 is closed.

In this modification, the size of the explosive 70 and its position within the shell 71, and the position of the shell 71 with respect to the base 76, are in accordance with the size, type'and strength of the pieces of material 92 and 95. When these adjustments are made, along with the adjustment of the ring 81, the charge 70 is detonated, the shock waves expanding therubber diaphragm 86 to contact the pieces 92 and 95 and to form them as shown by the solid lines of the pieces, the dotted lines showing the pieces before forming (see FIG. 10). The rubber diaphragm thus becomes the forming agent by the action of the shock waves. The openings'82 and 83 permit the pressure waves to pass into the atmosphere so that substantially only the shock waves do the rapid forming of the materials. Since the cavity 72 is not completely open to the atmosphere, any pressure within the cavity limits the return of the rubber diaphragm '86 into the cavity.

All of the above modifications utilize explosive shock waves rather than pressure waves, the shock waves being shown by the arrows 38 in FIG. 4. The curved cavities in the modifications shown in'FIGS. 5 and 6 and in the modification shown in FIGS. 8, 9, and 10 increase the efliciency of the apparatus by reflecting the shock waves to reinforce the waves directly from the explosive charges in the same manner as light waves in an optical system.

As mentioned above, this method and system of forming metals permits the formation of large pieces of material, and particularly brittle types of material of the new high heat resistant alloys which require rapid formmg.

I claim:

1. Material-forming apparatus for forming a piece of material into a predetermined shape comprising a die blockhaving a portion of said predetermined shape for supporting said piece of material and into which said piece of material is to be forced, a shell having a wave-reflecting cavity therein directed toward said piece of material, resilient means between said cavity and said piece of material for sealing said cavity, said die block being positioned opposite said. cavity, an explosive charge in said cavity, said wave-reflecting cavity having an opening to the free atmosphere providing an area of communication therebetween, means on said shell for adjusting the area of communication between said cavity and the free 'at-' mosphere for controlling the operating pressure within said cavity during the forming operation in accordance with the piece of material being formed, and means connectedto said explosive charge for detonating said charge to create shock waves within said cavity for impingement on said resilient means for forming said piece of material,

said waves being directed toward said piece of material.

2. The method of rapidly forming a piece ofmaterial into a predetermined shape comprising positioning said piece over theforming surface of a die having said predetermined shape, positioning an explosive charge in' a wave reflecting cavity directed toward said piece of material, and detonating said explosive charge to produce shock waves of a certain intensity, the intensity of said shock waves impinging on said material being predetermined in accordance with the pressure required to form said material, the predetermined intensity being effected by adjusting the area of communication between said cavity and the free atmosphere prior to detonating the charge so that portions of the waves produced upon detonation are released to the atmosphere, said shock Waves from said charge forcing said piece of material into said die.

3. The method in accordance with claim 2 in which said shock waves are impressed on a cavity-sealing resilient medium between said charge and said piece of material.

4. Material-forming apparatus comprising a shell having a substantially conical cavity therein, said shell having a mouth covered by a resilient diaphragm, an explosive charge mounted in said cavity for producing shock waves when exploded, means mounted on said apparatus for adjusting the position of said explosive charge in said cavity in accordance with the shock required to form said material, and die means positioned for supporting a material to be formed adjacent said mouth of said shell, said die means determining the final form of said material, said conical cavity reflecting certain of said shock waves to said material.

5. Material-forming apparatus in accordance with claim 4 in which a plurality of holes are positioned in said shell adjacent the mouth of said shell, an adjustable ring being positioned over said holes and having a similar plurality of holes therein, said holes in said ring coinciding with the holes in said shell when said ring is rotated to one adjusted position of said ring on said shell, the adjustment of said ring controlling the operative pressure in said cavity when said explosive charge is exploded.

6. Material-forming apparatus in accordance with claim 4 in which said resilient diaphragm is fixedly attached to the edge of said mouth of said shell.

References Cited in the file of this patent UNITED STATES PATENTS 939,702 Jones Nov. 9, 1909 2,367,206 Davis Jan. 16, 1945 2,586,706 Parr Feb. 19', 1952 2,648,125 McKenna et al Aug. 11, 1953 2,669,209 Hoifman Feb. 16, 1954 2,696,184 Demarest Dec. 7, 1954 2,703,297 MacLeod Mar. 1, 1955 2,762,734 Corral Sept. 11, 1956 2,849,977 Nielsen et al. Sept. 2, 1958 2,935,038 Chatten May 3, 1960 FOREIGN PATENTS 21,840 Great Britain of 1897 105,422 Sweden Sept. 8, 1942 115,846 Sweden Feb. 19, 1946 637,332 Great Britain May 17, 1950 30 Machinist, January 14, 1957, pages 112-115. 

